Is "Humans swallow an average of eight spiders per year in their sleep" true?
You supposedly swallow eight spiders a year while asleep, a factoid that spreads at parties precisely because it's disgusting enough to remember and repeat. It has no research behind it whatsoever. Spiders read a sleeping human's breathing, warmth, and vibration as danger, not shelter, and actively avoid crawling anywhere near it. Nobody has ever traced this claim back to an actual study, because one was never done.
What you were taught
Humans swallow an average of eight spiders per year in their sleep
What we know now
This claim is an urban legend with no evidence behind it. Spiders generally avoid sleeping humans, and there is no reason to believe people routinely swallow spiders while asleep.
Was "Humans swallow an average of eight spiders per year in their sleep" taught in school?
Yes — and not as a joke question on a quiz. This science claim showed up in textbooks, worksheets, and classroom posters through the 1980s, which is why so many people still remember it as settled fact long after the science moved on.
Is "Humans swallow an average of eight spiders per year in their sleep" true?
No. This claim is an urban legend with no evidence behind it. Spiders generally avoid sleeping humans, and there is no reason to believe people routinely swallow spiders while asleep. If you want the primary citation, start with Smithsonian - Do We Really Swallow Spiders in Our Sleep?
When was this understanding updated?
The evidence had largely shifted by around 1993. Schools don't flip overnight, though — plenty of classrooms kept teaching the older version for years after researchers had already moved on.